This new-investigator initiated (R01) resubmission, "Validity and Measurement Issues in Pathological Gambling", responds to a call for much needed attention to measurement and design challenges in mental health research. This is especially essential in pathological gambling (PG) research. National research efforts have recognized the need for consensus in the validity and assessment of PG across diverse populations (e.g., those with comorbid mental health and substance abuse conditions; NRC Report 1999). Critical to making these inroads is the development of rigorously tested tools for diagnosing the disorder, such as our research team's development of the computerized Gambling Assessment Module (C-GAM). The C-GAM addresses the criticisms of currently available assessments of PG. The currently proposed study adds a new dimension of validity to the Pl's NIDA (K01) Award design. The order of the clinical interview session will be randomly assigned to occur either one week before or one week after the two lab administered interviews. The clinical interview session includes administration of the semi-structured CGAM and a comprehensive personality assessment. Thus, the major aim of the proposed study is to establish diagnostic concordance of the structured, lay administered C-GAM interview to the semi structured, clinician administered C-GAM interview for the overall sample (n=150) and for several subgroups of gamblers varying by socio-demographics and psychiatric and substance abuse comorbidity. We will also evaluate the sensitivity and specificity of the C-GAM and explore the dimensionality of PG. As a methodology to further understand answers given in multiple interviews, we will evaluate discrepancies between the clinical and lay interviews, reasons for those discrepancies, and level of respondent understanding of these items. The proposed methodology is innovative in PG research and can potentially increase our understanding of PG disorder, thus aiding in future research and clinical efforts in refining diagnoses, establishing prevalence estimates, and identifying risk and protective factors associated with the development of comorbid mental health and substance use problems.